1. Field of the Invention
The present invention relates to a method of forming an electrically-conductive layer having excellent adhesiveness and uniformity, and an electroplating apparatus.
2. Background of the Related Art
The related art suggests several methods of forming metal-conductive oxide layers. For example, plasma vapor deposition, laser-induced reflow, chemical vapor deposition, electroless deposition and electroplating can create oxidation-proof, wear-proof decoration and wires in semiconductor devices. Of those methods, electroplating and electroless deposition provide high-quality conductive layers possessing excellent deposition characteristics at low process temperatures and low equipment costs.
Electroplating requires the formation of a thick, continuous seed layer on a surface of a plated body. Because the seed layer generates a conductive layer, a low resistance contact must form against the seed layer. For example, a chromium seed layer must be deposited on the stainless steel layer of a plated body in order to electroplate that stainless steel layer with nickel.
To form the seed layer, the solid surface is etched to remove impurities. Next, the plated body is placed in a plating bath containing electrolytes inside a process chamber to prevent formation of natural oxide. As shown in FIG. 1, a metallic seed layer 11 is formed on the surface of a plated body 10 by chemical vapor deposition (CVD) or sputtering, a physical vapor deposition (PVD) method. That seed layer 11 is oxidation-proof and contamination-resistant, and consists of the same or a different substance from the material used for the plated body 10.
Once the seed layer 11 forms, a plating bath is used to continue the electroplating process. That process involves a power supply, an electrolytic solution, a solid metal and a plated body 10. A positive terminal of the power supply connects to the solid metal, while a negative terminal of the power supply connects to the plated body 10. Once those terminal connections have been completed, the solid metal and the plated body 10 are dipped in the electrolyte solution, which contains an ionic species of the solid metal, to initiate the electroplating process.
When the power supply is transited to the xe2x80x98ONxe2x80x99 position, the ionic metal species in the electrolytic solution migrate to the negatively-charged plated body 10, and are deposited on that body to produce a plating layer 12 above the seed layer 11. That deposition process continues until a layer of desired thickness forms. The concentration of cations in the electrolyte solution is maintained as the metal dissolves in the electrolyte solution to compensate for the cations lost in the plating process.
A conductive metal or metal alloy layer as the plating layer 12 results from the electroplating process. The physical or chemical surface treatment of a surface of the plated body 10 before starting the electroplating process removes natural oxides, defects, organic/inorganic foreign contaminants, and impurities on the metal surface of the plated body, so as to form a desired uniform plating layer with strong adhesiveness to the plated body.
That surface treatment is necessary because contaminants and impurities interfere with the nucleation of plating material at the pristine stage. The contaminants and impurities deteriorate the uniformity of the conductive layer and its adhesiveness to the plated body 10. The adhesion between the plated body 10 and the conductive layer 12 is reduced because the space between the deposited metal grains increases because of the poor seed distribution on the plated body 10. As a result, the characteristics and quality of the plating layer 12 deteriorate. In contrast, less space between the grains corresponds with increased adhesion between the plated body 10 and the plating layer 12 and results in a higher quality metal layer with greater conductivity.
FIG. 4 shows a schematic drawing of a scanning electron microscope (SEM) image of a surface of an electroplating layer 12 formed by a related art. A plurality of metal grains 40, 41 grows to form the electroplated layer shown on a seed layer 42. Most of the grains 40, 41 are small in size, and the grain density per unit area is too low to form a highly adhesive, uniform surface. The grains 40, 41 continue to grow to fill in the spaces between the grains and form the plating layer as the whole grains connect to one another. Since the interfaces between the plating layer and the seed layer fail to provide sufficiently dense spaces among the grains, vacant spaces develop under the interfaces. The resulting deterioration of the adhesiveness between the seed layer and the plating layer is disadvantageous to forming a uniform layer.
However, as described above the related art has various disadvantages. The electroplating process of the related art is complicated because a surface of a plated body requires an additional process to conduct chemical surface treatment or to form a seed layer. To form a uniform plating layer, the seed layer requires an expensive metal that is difficult to contaminate. Additional complexities result from the poor adhesiveness between the plated body and the seed layer, as the grains are non-uniform and sparsely formed.
The above description and other related art of the electroplating process are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.
Accordingly, the present invention is directed to a method of forming a conductive layer and an electroplating device thereof that substantially obviates one or more limitations and disadvantages of the related art.
An object of the present invention is to provide a method of forming a conductive layer, and an electroplating device using same that provides a uniform conductive layer on a plated body.
Another object of the present invention is to provide a method of forming a conductive layer and an electroplating device using same that provides a conductive layer with excellent adhesion to a plated body.
Another object of the present invention is to provide a method of forming a conductive layer and an electroplating device using the same that uses supersonic waves.
Another object of the present invention is to provide a method of forming a conductive layer and an electroplating apparatus thereof that provides a uniform conductive layer with excellent adhesion to a plated body by adding a supersonic generator to an electroplating unit.
To achieve at least these and other objects and advantages in whole or in parts and in accordance with the purpose of the present invention, as embodied and broadly described, the present invention includes the steps of placing a sonic wave generator in an electrolyte solution, dipping a plated body connected to a negative terminal of a power supply with a switch and a plating body connected to a positive terminal of the power supply in the electrolyte solution where the power supply includes a switch, generating super sonic waves by operating the sonic wave generator, turning on the power supply by operating the switch, turning off the power supply by operating the switch after a predetermined time, and taking the plated body out of the electrolyte solution.
In a further aspect, the present invention includes a first bath filled with a liquid, a second bath filled with an electrolyte solution wherein the second bath is placed in the first bath, a sonic wave generator capable of propagating super sonic waves to the electrolyte solution, a power supply having a first and second terminals and a switch, a plated body connected electrically to the first terminal of the power supply, and a plating body connected electrically to the second terminal of the power supply where the plating body includes a substance that provides ions of the same species dissolved in the electrolyte solution.
In a further aspect, the present invention includes a plating bath filled with an electrolyte solution, a sonic wave generator dipped in the electrolyte solution, a power supply having a first and second terminals, a plated body connected electrically to the first terminal of the power supply, and a plating body connected electrically to the second terminal of the power supply, the plating body comprised of substance which provides ions the same as dissolved in the electrolyte solution.
In yet another aspect, the present invention includes a method for forming a conductive layer, comprising the steps of treating a plated body surface with supersonic waves and forming a plating layer on the treated plated body surface by electrochemistry.
In yet another aspect, the present invention includes an electroplating apparatus, comprising a first chamber containing an electrically conductive liquid, a generator that generates and propagates sonic waves, and a plated body, wherein the sonic waves impinge on the plated body.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.